These are the roots of trees, O monks, these are empty huts. Meditate, monks, do not be negligent, or else you will regret it later. This is our instruction to you.
Without approval and without scorn, but carefully studying the sentences word by word, one should trace them in the Discourses and verify them by the Discipline. If they are neither traceable in the Discourses nor verifiable by the Discipline, one must conclude thus: 'Certainly, this is not the Blessed One's utterance; this has been misunderstood by that bhikkhu - or by that community, or by those elders, or by that elder.' In that way, bhikkhus, you should reject it.
Your worst enemy cannot harm you as much as your own unguarded thoughts. Develop the mind of equilibrium. You will always be getting praise and blame, but do not let either affect the poise of the mind: follow the calmness, the absence of pride.
Sometime, somewhere you take something to be the truth. But if you cling to it too strongly, then even when the truth comes in person and knocks on your door, you will not open it.